LM5161: May you pls help check LM5161 circuit?

Hi Chen,

The schematic looks generally correct, although the 22uF/0805 caps may be low effective capacitance when 12V is applied.

I recommend using the LM5161 Fly-Buck quickstart calculator (download it from the product folder) to verify component values (particularly for ripple injection) This file is also useful to check current limit relative to the required load currents of the primary and secondary outputs.

Regards,

Tim

Hi Bogey,

Did you download LM5161 calculator to verify your circuit design?

http://www.ti.com/lit/zip/snvc200

Per my calculation on your application:

1. C365 is 0.01uF

2. T9 primary inductance is 115uH, current peak 0.85A

3. R280 is must to have to limit output voltage at no load condition.

B R

Andy

Hello Bogey,

Assuming you are using a 1:1 turns ratio "gapped" transformer with an Isat>1.9A and a leakage inductance<1% of Lprimary which should be around 120uH.  Also make sure the RC values across the transformer is 300kohm and 3.3nF.

Hope this helps?